1. Field of the Invention
This invention relates in general to progressing cavity pumps, and in particular to a progressing cavity pump installation in a well through tubing and using sucker rods for driving the pump.
2. Background of the Invention
A progressing cavity pump is a well known pump, frequently called a "Moineau" pump, that has an elastomeric outer element or stator. The stator has a double lead helix in its inner surface. A metal rotor having a single lead helical exterior inserts within the stator. When the rotor is rotated, it causes fluid to pump through the stator.
Progressing cavity pumps of this type are used for many purposes, particularly for pumping viscous liquids. These pumps are also used as oil well pumps. When used as an oil well pump, the stator is secured to the lower end of the well tubing, then lowered into the casing of the well. The rotor is secured to the lower end of the sucker rod and lowered through the tubing to position the rotor inside the stator. The sucker rod is rotated by means of a rotary power source at the surface. U.S. Pat. No. 2,267,459 shows one type of installation for an oil pump.
One disadvantage is that if the stator needs to be serviced, the string of tubing must be pulled. This is time consuming and requires special equipment. U.S. Pat. No. 3,347,169 shows a progressing cavity pump installation wherein the stator is lowered through the tubing on a flexible drive cable and secured by a seat.